SPring-8, the large synchrotron radiation facility

Speaker: Feng Ryan Wang, Ph.D.

Language: English

Affiliation: Department of Chemical Engineering, University College London

Title: Quantification and visualization statistics of Pt cathode degradation via correlative electron and X-ray imaging

Abstract:
Quantification and visualization of material degradation pathways and mechanisms are challenging. It is difficult to determine how microscopic chemical changes will collectively affect the macroscopic performance. Here we introduce a correlative electron and X-ray imaging method that enables multiscale (from 1 nm to 20 μm) quantification and visualization of Pt degradation pathways in the oxygen reduction reaction (ORR) for proton exchanges membrane fuel cells (PEMFC). Our correlative imaging performs statistics of 10⁷ Pt nanoparticles, provides two-dimensional (2D) information of Pt content, nanoparticle numbers, and movement tracking from 1 nm to 50 μm scale. With the accelerated durability test (ADT) in O₂ between 0.4 and 1.2 V vs reversible hydrogen electrode (RHE), the 2D nano-statistics reveal quantitatively: 1) 2:3 ratio between primary and secondary Pt degradation; 2) 3:4 ratio of activity loss from primary and secondary Pt degradation, which is regional depend. 3) Pt moves from centre to edge of carbon support at average of 1.6 ± 0.9 μm. We anticipate that these findings will be used to describe the collective nanoparticle behaviours in catalysis and other related applications. If time permits, I will also introduce our recent work in the design of Pt cathode catalysts and the use of in situ X-ray absorption fine structure (XAFS) to understand the dynamics of Pt alloy degradations.